Suspension Element for Linear Compressor

ABSTRACT

In a refrigeration compressor a pair of suspension elements support a linear compressor within a hermetic shell. Each suspension element includes a hub component is fixed to one of the compressor or shell. A substantially rigid ring is secured to the other of the compressor or shell, an elastic membrane extends across the area of the ring and is secured to the ring around its periphery. The hub component is secured to the membrane at the centre of the ring.

FIELD OF THE INVENTION

The present invention relates to linear compressors, and in particularlinear compressors of the type suitable for use in a vapour compressionrefrigeration system.

BACKGROUND TO THE INVENTION

Linear compressors of a type for use in a vapour compressionrefrigeration system are the subject of many documents in the prior art.One such document is our co-pending PCT patent applicationPCT/NZ2004/000108. That specification describes a variety ofdevelopments relating to compressors, many of which have particularapplication to linear compressors. The present invention relates tofurther improvements to compressor embodiments such as are described inthat patent application, which provides a general description of anexample compressor to which the present invention may be applied.However the present invention may also be applied beyond the scope ofthe particular embodiments of linear compressor disclosed in thatapplication. Persons skilled in the art will appreciate the generalapplication of the ideas herein to other embodiments of linearcompressors such as are found in the prior art.

PCT/NZ2004/000108 describes a number of arrangements for suspending alinear compressor assembly in a hermetic shell using coil springs.

The present invention relates generally to suspension elements forsuspending the compressor assembly within the hermetic shell not usingcoil springs.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a suspension elementwith improved characteristics with particular application to a linearcompressor and/or to provide refrigeration compressors incorporatingsuch elements, or to at least provide the industry with a useful choice.

In a first aspect the invention consists in a suspension element for usein supporting a linear compressor within a hermetic shell, said elementcomprising:

a hub component adapted for fixing to a first object,

a substantially rigid ring, and

an elastic membrane extending across the area of said ring and securedto said ring around its periphery,

said hub component being secured to said membrane at the centre of saidring.

According to a further aspect said membrane is moulded over said ring,and is moulded over at least a part of said hub component.

According to a further aspect said membrane comprises a natural orartificial rubber, polyurethane material, or rubber substitute.

In a further aspect the present invention consists in a refrigerationsystem compressor comprising a hermetic housing, a linear compressorwithin said hermetic housing, said compressor including at least tworelatively reciprocating parts, with one part typically being muchgreater mass than the other part, the relative reciprocation of thecentre of mass of each part occurring along an axis of reciprocation,and

at least a pair of suspension elements substantially as set forth in oneor more of the above paragraphs, the hub portion of each said suspensionelement being connected with said compressor part of greater mass, suchthat the centre of said hub at least substantially coincides with saidaxis of reciprocation, and the ring portion of each said element beingfixed to at least one part of said hermetic housing.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation in cross-section of a refrigerationcompressor including a linear compressor suspended in a housing. Thecompressor is suspended in the housing at each end by a suspensionelement according to a preferred embodiment of the present invention.

FIG. 2 is a perspective view of a suspension element according to afirst embodiment of the present invention.

FIG. 3 is a perspective view of a suspension element according to avariation of the invention where the membrane does not cover the entirearea bounded by the ring.

DETAILED DESCRIPTION

Referring to FIG. 1, the compressor for a vapour compressionrefrigeration system includes a linear compressor 1 supported inside ahousing 2. Typically the housing 2 is hermetically sealed and includes agases inlet port 3 and a compressed gases outlet port 4. Uncompressedgases flow within the interior of the housing surrounding the compressor1. These uncompressed gases are drawn into the compressor during intakestroke, compressed between the piston crown 14 and valve plate 5 on thecompression stroke, and expelled through discharge valve 6 into acompressed gases manifold 7. Compressed gases exit the manifold 7 to theoutlet port 4 in the shell through a flexible tube 8. To reduce thestiffness effect of discharge tube 8 the tube is preferably arranged asa loop or spiral transverse to the reciprocating axis of the compressor.The intake to the compression space may be through the piston (with anaperture and valve in the crown) or through the head, divided to includesuction and discharge manifolds and valves.

The illustrated linear compressor 1 has, broadly speaking, a cylinderpart and a piston part connected by a main spring. The cylinder partincludes cylinder chassis 10, cylinder head 11, valve plate 5 and acylinder liner 12. It also includes stator parts 15 for a linearelectric motor. An end portion 18 of the cylinder part, distal from thehead 11, mounts the main spring relative to the cylinder part. In theillustrated embodiment the main spring is a combination of coil spring19 and flat spring 20.

The piston part includes a hollow piston 22 with sidewall 24 and crown14. A rod 26 connects between the crown 14 and a supporting body 30 forlinear motor armature 17. The rod 26 has a flexible portion 28approximately at the centre of the hollow piston 22. The linear motorarmature 17 comprises a body of permanent magnet material (such asferrite or neodymium) magnetised to provide one or more poles directedtransverse to the axis of reciprocation of the piston within thecylinder liner. An end portion 32 of armature support 30, distal fromthe piston 22, is connected with the main spring 19, 20.

This briefly describes a linear compressor of a type for which thesuspension element of the present invention is useful. However it willbe appreciated that the usefulness of the suspension element of thepresent invention is not restricted to linear compressors of the typeand configuration illustrated. It is generally applicable whereoperation of the linear compressor results in the relative reciprocationof the centre of mass of the piston carrying part and the centre of massof the cylinder part along the linear axis.

The suspension element of the present invention is most usefully appliedto support the heavier of the relatively moving assemblies, typicallythe cylinder part assembly. In the preferred manner, such as illustratedin FIG. 1, a suspension element 40 is provided at each extreme end ofthe compressor. This is so that a centre of the suspension element canbe aligned with the axis of relative reciprocation of the centres ofmass of the two main assemblies.

The suspension element of the present invention is particularly adaptedfor a linear compressor, which exhibits a linear oscillating motionrather than a planar oscillating motion. An isolating suspension element40 is provided at either end of the compressor.

In the preferred embodiments illustrated in FIGS. 2 and 3, eachsuspension element 40 includes an elastic membrane 42. The elasticmembrane 42 spans between a central hub 44 and a surrounding ring 46.One of the hub or ring is fixed to the compressor. The other of the hubor ring is fixed to the compressor shell. Fixing the surrounding ring 46to the compressor is most likely to be convenient. In the embodimentillustrated, the central hub 44 is connected to the compressorsubstantially on the centreline so that the plane of the membrane 42 isperpendicular to and intersects the centreline of the compressor. Thesupporting ring 46 assists with assembly of the compressor, allowing thecompressor assembly to be placed into a lower half shell fullysupported, with the upper half shell subsequently fitted.

The hub 44 is adapted for connection to the compressor. For example thehub 44 may include one or more apertures 43 for receiving a fastener orfasteners, or may include a suitable clip for engaging a suitablecomplementary feature on the compressor.

Referring to FIG. 1, the ring 46 is preferably fitted within a suitablereceptacle of the housing. For example an annular groove 53 in theinside surface 55 of the housing may retain the ring. One half of theannulus of the groove may be formed in each half of the housing and thering may be captured in the groove as the housing is assembled. A numberof open clips in each half of the housing could be provided instead of acontinuous groove.

Each membrane suspension element 40 is preferably arranged in thehousing with the hub 44 secured to a respective end of the compressorassembly. The suspension element is arranged such that the plane of themembrane 42 is fully perpendicular to the axis of reciprocation of thecompressor.

In a variation, illustrated in FIG. 3, the membrane 42 may not cover thewhole area defined by the ring. The membrane may include a plurality ofseparate sections (spokes) 57 extending from hub 44 to ring 46 or themembrane may include a plurality of openings 59 distributed around thearea between hub and ring.

The membrane 42 may be a high performance natural or artificial rubberor polyurethane material, or other material having suitable elasticproperties. Examples include natural rubber, Sunprene (a polypropyleneand natural rubber composite available from DuPont) or thermoplasticrubber. The material may be moulded over the outer ring component.

The outer ring component 46 may be of steel or other suitable rigidmaterial.

The membrane 42 may also be moulded over the hub component 44, which maybe any suitable material, and include any suitable adaptation forfacilitating fixing to the compressor.

1. A suspension element for use in supporting a linear compressor withina hermetic shell, said element comprising: a hub component adapted forfixing to a first object, a substantially rigid ring, and an elasticmembrane extending across the area of said ring and secured to said ringaround its periphery, said hub component being secured to said membraneat the centre of said ring.
 2. A suspension element as claimed in claim1 wherein said membrane is moulded over said ring, and is moulded overat least a part of said hub component.
 3. A suspension element asclaimed in claim 1 wherein said membrane comprises an artificial rubberor polyurethane material.
 4. A suspension element as claimed in claim 2wherein said membrane comprises an artificial rubber or polyurethanematerial.
 5. A refrigeration system compressor comprising a hermetichousing, a linear compressor within said hermetic housing, saidcompressor including at least two relatively reciprocating parts, withone part typically being much greater mass than the other part, therelative reciprocation of the centre of mass of each part occurringalong an axis of reciprocation, and at least a pair of suspensionelements each comprising: a hub component adapted for fixing to a firstobject, a substantially rigid ring, and an elastic membrane extendingacross the area of said ring and secured to said ring around itsperiphery, said hub component being secured to said membrane at thecentre of said ring, the hub portion of each said suspension elementbeing connected with said compressor part of greater mass, such that thecentre of said hub at least substantially coincides with said axis ofreciprocation, and the ring portion of each said element being fixed toat least one part of said hermetic housing.
 6. A refrigeration systemcompressor as claimed in claim 5 wherein said membrane is moulded oversaid ring, and is moulded over at least a part of said hub component. 7.A refrigeration system compressor as claimed in claim 5 wherein saidmembrane comprises an artificial rubber or polyurethane material.
 8. Arefrigeration system compressor as claimed in claim 6 wherein saidmembrane comprises an artificial rubber or polyurethane material.